Catalytic carbonylation of olefinic and acetylenic compounds to form oxygenated derivatives with an increased content of carbon atoms is a well-established technology. Various developments and improvements are described in U.S. Pat. Nos. such as 2,768,968; 2,863,911; 2,876,254; 3,040,090; 3,455,989; 3,501,518; 3,507,891; 3,652,655; 3,660,439; 3,700,706; 3,723,486; 3,746,747; 3,755,419; 3,755;421; 3,793,369; 3,856,832; 3,859,319; 3,887,595; 3,906,015; 3,917,677; 3,952,034; 3,992,423; 4,102,920; 4,245,115; 4,246,183; and references cited therein.
Of particular interest with respect to the present invention is the chemical literature relating to dimeric carbonylation of aliphatic conjugated dienes in the presence of a hydroxylated coreactant and a catalyst complex of a Group VIII noble metal and a Group VA tertiary donor ligand. The dimeric carbonylation reaction is illustrated by the following chemical equation with respect to the interaction of 1,3-butadiene with alkanol: ##STR1##
In a report published in Tetrahedron, 28, 3721 (1972), there is described a dimeric carbonylation of 1,3-butadiene in the presence of alkanol and a palladium-phosphine complex catalyst to yield alkyl 3,8-nonadienoate. The publication discloses that the absence of halide coordinated to the palladium metal is essential for the formation of alkyl nonadienoate product. In the presence of halide, one mole of 1,3-butadiene reacts with one mole of carbon monoxide and one mole of alkanol to yield alkyl 3-pentenoate.
U.S. Pat. No. 4,124,617 describes a process for the selective production of fatty acid derivatives from aliphatic diene substrates, in the presence of dual-function homogeneous palladium complexes and certain classses of organic tertiary nitrogen bases. One aspect of this type of process is that the use of tertiary nitrogen bases promotes the production of various byproducts such as C.sub.5 -esters. Another aspect is that the catalyst tends to exhibit a reaction rate decrease during the course of the carbonylation reaction due to instability of the catalyst system.
Further, in processes for dimeric carbonylation of aliphatic conjugated dienes such as are disclosed above, the dimeric product is separated from the catalyst complex and other components of the reaction product mixture employing conventional techniques such as distillation. In such product recovery procedures some of the catalyst complex (e.g., palladium-phosphine complex) is lost by precipitation, and more significantly, the catalyst complex invariably suffers from a loss of reactivity. This is a serious consequence for purposes of a catalyst complex which is intended to be recovered and recycled in a dimeric carbonylation process. The efficiency of the process is dependent on the stability and reactivity of the catalyst system.
Accordingly, it is a main object of this invention to provide an improved process for conversion of aliphatic conjugated dienes into fatty acid derivatives.
It is another object of this invention to provide a process for producing alkyl nonadienoate by dimeric carbonylation of 1,3-alkadiene with improved conversion and selectivity.
It is a further object of this invention to provide a stabilized palladium catalyst solution adapted for carbonylation of olefinic hydrocarbons.
Other objects and advantages of the present invention shall become apparent from the accompanying description and illustrative processing data.